Abstract
These lectures survey some recent developments concerning the theory and applications of harmonic approximation in Euclidean space. We begin with a discussion of the significance of the concept of thinness for harmonic approximation, and present a complete description of the closed (possibly unbounded) sets on which uniform harmonic approximation is possible. Next we demonstrate the power of such results by describing their use to solve an old problem concerning the Dirichlet problem for unbounded regions. The third lecture characterizes the functions on a given set which can be approximated by harmonic functions on a fixed open superset. Finally, we return to applications, and explain how some problems concerning the boundary behaviour of harmonic functions have recently been solved using harmonic approximation.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
N. U. Arakelyan, Uniform and tangential approximations by analytic functions, Izv. Akad. Nauk Armjan. SSR Ser. Mat. 3 (1968), 273–286 (Russian); English translation, Amer. Math. Soc. Transl. (2) 122 (1984), 85-97.
N. U. Arakelyan, Approximation complexe et propriétés des fonctions analytiques, Actes, Congrès intern. Math. (1970), Tome 2, 595–600.
D. H. Armitage, Uniform and tangential harmonic approximation, These proceedings.
D. H. Armitage and S. J. Gardiner, Classical Potential Theory, Springer, London, 2001.
D. H. Armitage and M. Goldstein, Tangential harmonic approximation on relatively closed sets, Proc. London Math. Soc. (2) 68 (1994), 112–126.
M. G. Arsove, The Lusin-Privalov theorem for subharmonic functions, Proc. London Math. Soc. (3) 14 (1964), 260–270.
T. Bagby and P. M. Gauthier, Approximation by harmonic functions on closed subsets of Riemann surfaces, J. Anal. Math. 51 (1988), 259–284.
T. Bagby and P. M. Gauthier, Harmonic approximation on closed subsets of Riemannian manifolds, in: Complex Potential Theory (P. M. Gauthier, ed.), NATO ASI Ser. C Math. Phys. Sci. 439, Kluwer, Dordrecht, 1994; 75–87.
T. Bagby, P. M. Gauthier and J. Woodworth, Tangential harmonic approximation on Riemannian manifolds, in: Harmonic Analysis and Number Theory (S. W. Drury and M. Ram Murty, eds.), CMS Conf. Proc. 21, Amer. Math. Soc, Providence, RI, 1997; 58–72.
R. D. Berman, A converse to the Lusin-Privalov radial uniqueness theorem, Proc. Amer. Math. Soc. 87 (1983), 103–106.
B. Böe, Sets of determination for smooth harmonic functions, preprint.
M. Brelot, Sur l’approximation et la convergence dans la théorie des fonctions har-moniques ou holomorphes, Bull. Soc. Math. France 73 (1945), 55–70.
T. Carleman, Sur un théorème de Weierstrass, Ark. Mat. Astronom. Fys. 20B (1927), 1–5.
Chen Huaihui and P. M. Gauthier, A maximum principle for subharmonic and plurisub-harmonic functions, Canad. Math. Bull. 35 (1992), 34–39.
A. Debiard and B. Gaveau, Potentiel fin et algebres de fonctions analytiques I, J. Funct. Anal. 16 (1974), 289–304.
J. Deny, Sur l’approximation des fonctions harmoniques, Bull. Soc. Math. France 73 (1945), 71–73.
J. Deny, Systèmes totaux de fonctions harmoniques, Ann. Inst. Fourier (Grenoble) 1 (1949), 103–113.
M. R. Essén and S. J. Gardiner, Limits along parallel lines and the classical fine topology, J. London Math. Soc. (2) 59 (1999), 881–894.
B. Fuglede, Finely Harmonic Functions, Lecture Notes in Math. 289, Springer, Berlin, 1972.
B. Fuglede, Asymptotic paths for subharmonic functions, Math. Ann. 213 (1975), 261–274.
B. Fuglede, Fine potential theory, Mitt. Math. Ges. DDR 2-3 (1986), 3–21.
S. J. Gardiner, The Dirichlet problem with non-compact boundary, Math. Z. 213 (1993), 163–170.
S. J. Gardiner, Superharmonic extension and harmonic approximation, Ann. Inst. Fourier (Grenoble), 44 (1994), 65–91.
S. J. Gardiner, Tangential harmonic approximation on relatively closed sets, Illinois J. Math. 39 (1995), 143–157.
S. J. Gardiner, Harmonic Approximation, London Math. Soc. Lecture Note Ser. 221, Cambridge Univ. Press, Cambridge, 1995.
S. J. Gardiner, The Lusin-Privalov theorem for subharmonic functions, Proc. Amer. Math. Soc. 124 (1996), 3721–3727.
S. J. Gardiner, Decomposition of approximable harmonic functions, Math. Ann. 308 (1997), 175–185.
S. J. Gardiner, Non-tangential limits, fine limits and the Dirichlet integral, to appear in Proc. Amer. Math. Soc.
S. J. Gardiner and M. Goldstein, Carleman approximation by harmonic functions, Amer. J. Math. 117 (1995), 245–255.
S. J. Gardiner and W. Hansen, Boundary sets where harmonic functions may become infinite, preprint.
P. M. Gauthier and S. Ladouceur, Uniform approximation and fine potential theory, J. Approx. Theory 72 (1993), 138–140.
M. V. Keldys, On the solvability and stability of the Dirichlet problem, Uspekhi Mat. Nauk 8 (1941), 171–231 (Russian); English translation Amer. Math. Soc. Transl. 51 (1966), 1-73.
M. Labrèche, De l’approximation harmonique uniforme, Doctoral thesis, Université de Montréal, 1982.
N. N. Lusin and I. I. Privalov, Sur l’unicité et la multiplicité des fonctions analytiques, Ann. Sci. École Norm. Sup. (3) 42 (1925), 143–191.
A. A. Nersesyan, Carleman sets, Izv. Akad. Nauk. Armjan. SSR Ser. Mat. 6 (1971), 465–471 (Russian); English translation Amer. Math. Soc. Transl. (2) 122 (1984), 99-104.
R. Nevanlinna, Über eine Erweiterung des Poissonschen Integrals, Ann. Acad. Sci. Fenn. Ser.A 24 (4) (1925), 1–15.
P. J. Rippon, The boundary cluster sets of subharmonic functions, J. London Math. Soc. (2) 17 (1978), 469–479.
A. Stray, Decomposition of approximable functions, Ann. Math. 120 (1984), 225–2
A. Stray, Simultaneous approximation in the Dirichlet space, to appear in Math. Scand.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2001 Springer Science+Business Media Dordrecht
About this chapter
Cite this chapter
Gardiner, S.J. (2001). Harmonic approximation and its applications. In: Arakelian, N., Gauthier, P.M., Sabidussi, G. (eds) Approximation, Complex Analysis, and Potential Theory. NATO Science Series, vol 37. Springer, Dordrecht. https://doi.org/10.1007/978-94-010-0979-9_7
Download citation
DOI: https://doi.org/10.1007/978-94-010-0979-9_7
Publisher Name: Springer, Dordrecht
Print ISBN: 978-1-4020-0029-4
Online ISBN: 978-94-010-0979-9
eBook Packages: Springer Book Archive